Process for providing a magnetic recording transducer having a smooth magnetic seed layer

ABSTRACT

A method for providing a magnetic recording transducer is provided. The method includes providing a substrate, and a magnetic shield having a top surface above the substrate. The top surface is treated by a first plasma treatment performed at a first power. An amorphous ferromagnetic (FM) layer is deposited on and in contact with the top surface to a thickness of at least 5 Angstroms and not more than 50 Angstroms. A second plasma treatment is performed at a second power. A magnetic seed layer is provided on and contact with the amorphous FM layer. The magnetic seed layer may comprise a bilayer. A nonmagnetic spacer layer is provided above the magnetic seed layer, an antiferromagnetic (AFM) layer provided above the spacer layer, and a read sensor provided above the AFM layer.

BACKGROUND OF THE INVENTION

Disk drives typically use heads residing on sliders to read from andwrite to the magnetic media. Read and write transducers residing in thehead are flown at a small, controlled spacing above the magnetic medium(disk) during read and write operations. An air bearing forms betweenthe head and the disk due to the disk rotating at high speeds to providecontrolled head to disk spacing. Magnetic fields emanating from thewrite transducer pole tip switches magnetization of the magnetic medium,i.e., writing to the medium. Among other factors, a smaller and moretightly controlled magnetic writing field will allow more data to bewritten in the same space, thereby increasing areal density.

FIG. 1 illustrates a side section view of read/write head 100incorporating a write transducer 150 and read transducer 110, bothfacing the ABS 190. The read transducer 110 may include shield 111 andshield 113 as well as read sensor 112. Write transducer 150 includesshield 114, main pole 101, assist pole (or auxiliary pole) 101′, coil140 and coil 140′, leading shield 117 and trailing shield 120. Sideshields are not shown in this sectional view, however may reside on thesides of main pole 101. Main pole 101 has trailing bevel 101 a and aleading bevel 101 b. A leading nonmagnetic gap layer 104 separates mainpole 101 from underlying structures, and trailing nonmagnetic gap layer105 separates main pole 101 from structures above. A nonmagnetic spacerlayer 102 is illustrated on the non-beveled section of main pole 101;however, in other embodiments may be provided above main pole 101beginning at any point distal from the ABS 190, including on bevel 101a.

FIG. 2 illustrates an ABS view of a read transducer section 200analogous to read sensor 110 described in FIG. 1. A read sensor 260 ispositioned between magnetic bottom shield 250 and magnetic top shield280 and between side shield 274 and 274′. In one embodiment, nonmagneticlayers 275 and 275′ may be applied above side shields 274 and 274′respectively. The addition of nonmagnetic layers 275 and 275′ may bedesirable to separate a side shield comprising a hard bias from a softmagnetic material in magnetic top shield 280 above. A nonmagnetic gaplayer 273 is analogous to nonmagnetic gap layer 105 in FIG. 1.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a side section view of a portion of a read-writerecording head.

FIG. 2 illustrates an ABS section view of a read transducer portion of arecording head.

FIG. 3 illustrates a view of a read transducer comprising multiplelayers positioned between shields in accordance with one embodiment ofthe invention.

FIG. 4 illustrates a fabrication detail of a bottom portion of a readtransducer in accordance with one embodiment of the invention.

FIG. 5 illustrates a process for fabricating a recording transducer inaccordance with one embodiment of the invention.

FIG. 6 is a graph showing performance characteristics of a recordingtransducer in accordance with one embodiment of the invention.

FIG. 7 is a graph showing performance characteristics of a recordingtransducer in accordance with one embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

In the following detailed description, numerous specific details are setforth to provide a full understanding of the present invention. It willbe apparent, however, to one ordinarily skilled in the art that thepresent invention may be practiced without some of these specificdetails. In other instances, well-known structures and techniques havenot been shown in detail to avoid unnecessarily obscuring the presentinvention. References to top, side, bottom, or similar terms are usedfor descriptive purposes with reference to the figures and descriptionsand should not be taken as limiting the scope of the invention.

FIG. 3 illustrates a view of a read transducer 300 comprising multiplelayers positioned between shields, and is an embodiment analogous to onedescribed generally in FIG. 2; however, the side structures are notdepicted. A bottom shield 320 resides on a substrate 301. The substrate301 may be any suitable underlayer and may include, for example, alumina(ALOx). A read sensor 310 resides above bottom shield 320. Bottom shield320 may comprise soft magnetic material. A top shield 390 resides aboveand magnetically shields the read sensor 310. Top shield 390 maycomprise soft magnetic material and in one embodiment comprises the samesoft magnetic material as in bottom shield 320.

In one embodiment of the invention, read sensor 310 comprises magneticseed layer(s) 330, spacer layer 340, AFM layer 350, pinned layer 355,and AFM coupling (AFC) layer 360. In one embodiment of the invention,AFM Layer 350 may comprise one of IrMn, RhMn, RuMn, or FeMn; and inanother embodiment may comprise one of PdMn, NiMn, or PtMn if a higherblocking temperature is desired. Spacer layer 340 functions tomagnetically separate the magnetic seed layer(s) 330 from AFM layer 350,so the magnetic seed layer 330 won't be pinned by AFM layer 350. In anembodiment of the invention, the magnetic seed layer 330 comprises abilayer. In one embodiment of the invention, spacer layer 340 maycomprise, for example, Ru, Ti, or Ta, or their combinations.

Pinned layer 355 is above AFM layer 350 and may comprise, for example,CoFe or CoFeB. The AFM layer 350 stabilizes the pinned layer 355. Themagnetization (not shown) of pinned layer 355 is substantially fixed, orpinned. The magnetization is fixed by annealing the read sensor 310, ora portion thereof, in an oriented magnetic field at an annealingtemperature. AFC layer 360 is above pinned layer 355 and providesanti-parallel alignment from the pinned layer 355 to reference layer 375above, and may comprise, for example, Ru.

A barrier layer 380 is above reference layer 375 and a free layer 385above barrier layer 380. A capping layer 386 is above free layer 385.The read sensor 310 has a resistance that varies in response to therelative magnetic orientations of the reference layer 375 below thebarrier layer 380, and the free layer 385 above the barrier layer 380.The orientation of free layer 385 may move, or switch, in response to anexternal field such as that from a magnetic recording medium. A sensecurrent may be passed between bottom shield 320 and top shield 390; andas the magnetic field emanating from the recording medium passes thefree layer 385, the resistance changes, thereby affecting the sensecurrent, which may be used to provide an electrical signal. Thisconfiguration is referred to as current perpendicular to plane (CPP),although other configurations known in the art such as current in plane(CIP) may also be used. Other and/or different components may befabricated in other embodiments. For example, in some embodiments,coupling enhancing layers, stop layers and/or seed layers may alsoremain between layers as part of the fabrication process.

FIG. 4 illustrates a fabrication detail of a bottom portion 400 of aread transducer in accordance with one embodiment of the invention. InFIG. 4, bottom shield 420 is analogous to bottom shield 320 in FIG. 3,magnetic seed layer 430 is analogous to magnetic seed layer 330 in FIG.3, and spacer layer 440 is analogous to spacer layer 340 in FIG. 3.Magnetic seed layer 430 also includes an amorphous FM layer 432 on topof magnetic shield 420.

Also shown in FIG. 4 is a plasma treatment 420A that is performed afterthe chemical mechanical polishing (CMP) of the bottom shield 420. CMPprovides a smooth surface and may leave a surface roughness R_(a(1))from about 0.2 nm to about 0.4 nm. Unfortunately, after the CMP process,oxidation residue may form on the surface that may interfere, or cause aboundary with a magnetic seed layer formation to be applied over thebottom shield 420. In order to eliminate this residue, the bottom shield420 is treated with a first plasma treatment 420A prior to deposition ofadditional layers. The bottom shield 420 is exposed to gaseous plasma ata first power from approximately 30 Watts to approximately 100 Watts. Inone embodiment of the invention, the first plasma treatment is performedusing physical vapor deposition (PVD) technology and for a durationsufficient to remove CMP residue and expose the underlying bottom shield420. One consequence of the first plasma treatment is that the plasmatreatment will affect the smooth crystalline surface of shield 420 andleave a roughened surface. For example, the surface roughness R_(a(2))may be increased, and may be above about 0.4 nm after the plasmacleaning treatment.

In one embodiment of the invention, an amorphous FM layer 432 is applieddirectly on and in contact with the plasma treated bottom shield 420. Inone embodiment, the amorphous FM layer 432 comprises at least one ofCoFeB, NiCoFeB, and NiFeB, wherein B comprises from about 18 atomicpercent (at. %) to about 22 at. %. In one embodiment, the amorphousferromagnetic (FM) layer 432 is deposited on and in contact with thebottom shield 420; and the amorphous FM layer 432 deposited to a firstthickness of at least 5 Angstroms and not more than 50 Angstroms; and inone embodiment, the amorphous FM layer 432 is deposited to a firstthickness of about 20 Angstroms. Because the amorphous FM layer 432 isamorphous, it has the effect of providing a surface that can besmoothened significantly by appropriate plasma treatment, therebysmoothing the roughened surface of bottom shield 420, and providing animproved surface for layers to be applied above.

Amorphous FM layer 432 was deposited to a first thickness greater than afinal thickness to allow for a second plasma treatment 432A thatprovides both smoothing and thinning of amorphous FM layer 432. In oneembodiment of the invention, the second plasma treatment 432A isperformed at a second power that may be from approximately 30 Watts toapproximately 50 Watts. In another embodiment, the second plasmatreatment reduces the thickness of the amorphous FM layer 432 to a finalthickness of at least 5 Angstroms and not more than 20 Angstroms.

After the second plasma treatment 432A, the bilayer magnetic seed layer438 is deposited on the plasma treated amorphous FM layer 432. In oneembodiment of the invention, the magnetic seed layer 438 is a bilayerincluding a first magnetic seed layer 434, the first magnetic seed layeron and in contact with the amorphous FM layer 432, and a second magneticseed layer 436 that is on and in contact with the first magnetic seedlayer 434, wherein the first magnetic seed layer 434 comprisesNi_(1-x)Fe_(x), where x is at least 0.45 and not more than 0.55 and thesecond magnetic seed layer 436 comprises Ni_(1-y)Fe_(y) where y is atleast 0.05 and not more than 0.15.

Use of the bilayer magnetic seed layer 438 may improve performance ofthe read sensor 310 and thus the read transducer 300. The first magneticseed layer 434 has a higher concentration of Fe. The higherconcentration of Fe results in a higher thermal stability in the readsensor 310. As a result, the stability of the read sensor 310 may beimproved. The second magnetic seed layer 436 has a lower concentrationof Fe than the first magnetic seed layer 436. The second magnetic seedlayer 436 thus has a lower magnetic moment than the first magnetic seedlayer 434. As a result, issues due to a high moment of the magnetic seedlayer 438 such as issues due to over-milling may be reduced. Inaddition, the second magnetic seed layer 436 may have magnetostrictionopposite to that of the first magnetic seed layer 434. For example, thesecond magnetic seed layer 436 layer may have negative magnetostriction,while the first magnetic seed layer has a positive magnetostriction. Thetotal magnetostriction of the bilayer magnetic seed layer 438 may thusbe reduced or brought to zero by balancing the magnetostriction. Thus,the bilayer magnetic seed layer 438 may be less likely to induceunwanted anisotropies, improving the stability of the shield 420.Consequently, performance of the read transducer 300 may be improved.

Spacer layer 440 may comprise nonmagnetic material; and may comprise atleast one of Ru, Ti, and Ta. In some embodiments, the spacer layer 440may be used to break or reduce the magnetic coupling between the bilayermagnetic seed layer 438 and the AFM layer 350. In one embodiment, thenonmagnetic spacer layer 440 is deposited to a final thickness of atleast 2.0 Angstroms and not more than 4.0 Angstroms prior to depositingthe AFM layer 350. The nonmagnetic spacer layer cannot exceed a maximumthickness otherwise the magnetic exchange field (H_(ex)) will decreaseand the sensor may become unstable. The present invention improvesH_(ex) by improving the crystalline structure and thereby improvesstability of the AFM layer 350. This, in turn, allows for greaterthickness range in the thickness of the spacer layer 440, and furtherresulting in an improved magnetic resistance ratio (MR) and highersensor performance.

FIG. 5 illustrates a process 500 for fabricating a magnetic recordingtransducer having a smooth magnetic seed layer.

Beginning in block 501, a bottom shield comprising soft magneticmaterial is provided. Typically, the bottom shield comprises NiFe, andis provided on a substrate which may comprise AlTiC. The bottom shieldundergoes patterning and planarization, typically CMP, in preparationfor subsequent operations to deposit a read sensor above the bottomshield.

In block 510, the bottom shield is exposed to gaseous plasma in a firstplasma treatment. The first plasma treatment is a cleaning operationperformed prior to deposition of additional layers. The bottom shieldmay be exposed to gaseous plasma in a first plasma treatment process ata first power from approximately 30 Watts to approximately 100 Wattsuntil residue and oxidation are substantially removed from the bottomshield.

In block 520, an amorphous FM layer is deposited on the plasma treatedbottom shield. The amorphous FM layer may be deposited to a thicknessgreater than a final desired thickness. In one embodiment of theinvention, the amorphous FM layer is deposited to a thickness of about20 Angstroms.

In block 530, the amorphous FM layer is treated with low power gaseousplasma in a second plasma treatment operation. The second plasmatreatment process may be at a power from approximately 30 Watts toapproximately 50 Watts, and continues until a final target thickness isachieved. In one embodiment, the final target thickness of the amorphousFM layer may be about 10 Angstroms.

In block 540, a first magnetic seed layer is deposited on and in contactwith the plasma treated amorphous FM layer.

In block 550, a second magnetic seed layer is deposited on the firstmagnetic seed layer.

In block 560, a nonmagnetic spacer layer is deposited above the secondmagnetic seed layer. In one embodiment, the nonmagnetic seed layer maycomprise at least one of Ru, Ti, and Ta, and may have a final thicknessof at least 2.0 Angstroms and not more than 4.0 Angstroms.

In block 570, an AFM layer is deposited on the nonmagnetic spacer layer.

In block 580, the remaining sensor layers are provided above the AFMlayer.

FIG. 6 is a chart that illustrates the performance of a read sensorfabricated according to embodiments of the invention. The y-axis in FIG.6 is the magnetoresistance ratio measured in percent (MR %), computed asmaximum magnetoresistance minus the minimum magnetoresistance, thedifference divided by the minimum magnetoresistance, and the resultmultiplied by 100%. The x-axis of FIG. 6 is the resistance area (RA)measured in Ohms micron². It is generally desired to have a high MR % toprovide a high signal to noise ratio (SNR).

The first response curve 601 represents the transfer function of a readsensor similar to that described in FIG. 3, and including a first plasmatreatment on the bottom shield similar to that described in first plasmatreatment 420A in FIG. 4; and also including an amorphous FM layersimilar to the amorphous FM layer 432 in FIG. 4. Response curve 601 doesnot; however, include a second plasma treatment on the amorphous FMlayer.

The second response curve 602 represents the transfer function of a readsensor according to one embodiment of the invention. Second responsecurve 602 illustrates the response of a read sensor similar to thatdescribed in FIG. 3 and FIG. 4, and including the first plasma treatment420A and the second plasma treatment 432A and fabricated using process500 as described in FIG. 5.

The response curve 601 demonstrates that as the read sensor RA isreduced below about 0.5, that the MR % is significantly degraded,limiting the amount the physical size of the read transducer can bereduced and still provide a high performance transducer. The responsecurve 602, however, illustrates a significantly higher MR %, and alsohigh performance at a much smaller RA. This combination of higher MR %at even smaller RA enable the fabrication of smaller read transducersthat are able to sense higher density magnetic patterns emanating from arecorded magnetic media, thereby increasing the achievable areal densityof the magnetic storage device. Another favorable factor includes asignificant increase of SNR.

FIG. 7 is a chart that illustrates the performance of a read sensorfabricated according to embodiments of the invention. The y-axis in FIG.7 is the pinning strength H_(ex) of the AFM layer measured in Oersteads(Oe). The x-axis is the thickness of the spacer layer above the magneticseed layer measured in Angstroms.

The first response curve 701 represents the transfer function of a readsensor similar to that described in FIG. 3, and including a first plasmatreatment on the bottom shield similar to that described in first plasmatreatment 420A in FIG. 4; and also including an amorphous FM layersimilar to the amorphous FM layer 432 in FIG. 4. Response curve 701 doesnot; however, include a second plasma treatment on the amorphous FMlayer.

The second response curve 702 represents the transfer function of a readsensor according to one embodiment of the invention. Second responsecurve 702 illustrates the response of a read sensor similar to thatdescribed in FIG. 3 and FIG. 4, and including the first plasma treatment420A and the second plasma treatment 432A and fabricated using process500 as described in FIG. 5.

It can be seen that in response curve 701 that spacer layer is verysensitive to thickness and becomes unstable above a thickness of about3.5 Angstroms, where the response curve ends. The thickness of thespacer layer also significantly affects the H_(ex), and thereforebecomes a factor in how small, or thin, the sensor stack can befabricated between the top shield and the bottom shield. This narrowuseful range is also harder to fabricate.

In response curve 702, the curve is shifted upward from response curve701, representing the improved H_(ex) that results from the improved AFMlayer, which in turn resulted from the process treatments previouslydescribed in FIG. 4. Additionally, it can be seen from response curve702 that the spacer layer may be fabricated substantially thicker thatwas previously possible, while remaining stable. The thickness of thespacer layer may now be extended from a thickness below about 3.4Angstroms, to a thickness of at least 3.6 angstroms. This extendedusable range also has the effect of increasing process margin.Thicknesses between about 3.6 and 4.0 Angstroms shown as dotted responsecurve 702′ are also stable under some conditions; for example, dependingon the thickness of the AFM layer.

The description of the invention is provided to enable any personordinarily skilled in the art to practice the various embodimentsdescribed herein. While the present invention has been particularlydescribed with reference to the various figures and embodiments, itshould be understood that these are for illustration purposes only andshould not be taken as limiting the scope of the invention.

There may be many other ways to implement the invention. Variousfunctions and elements described herein may be partitioned differentlyfrom those shown without departing from the spirit and scope of theinvention. Various modifications to these embodiments will be readilyapparent to those ordinarily skilled in the art, and generic principlesdefined herein may be applied to other embodiments. Thus, many changesand modifications may be made to the invention, by one having ordinaryskill in the art, without departing from the spirit and scope of theinvention.

A reference to an element in the singular is not intended to mean “oneand only one” unless specifically stated, but rather “one or more.” Theterm “some” refers to one or more. Underlined and/or italicized headingsand subheadings are used for convenience only, do not limit theinvention, and are not referred to in connection with the interpretationof the description of the invention. All structural and functionalequivalents to the elements of the various embodiments of the inventiondescribed throughout this disclosure that are known or later come to beknown to those of ordinary skill in the art are expressly incorporatedherein by reference and intended to be encompassed by the invention.Moreover, nothing disclosed herein is intended to be dedicated to thepublic regardless of whether such disclosure is explicitly recited inthe above description.

We claim:
 1. A method for providing a magnetic recording transducerhaving a magnetic seed layer comprising: providing a substrate;providing a magnetic shield having a first top surface above thesubstrate; treating the first top surface by a first plasma treatmentperformed at a first power; depositing an amorphous ferromagnetic (FM)layer on and in contact with the first top surface, the amorphous FMlayer deposited to a thickness of at least 5 Angstroms and not more than50 Angstroms; reducing the thickness of the amorphous FM layer by asecond plasma treatment performed at a second power; providing amagnetic seed sublayer on and in contact with the amorphous FM layer,the magnetic seed layer including the amorphous FM layer and themagnetic seed sublayer; providing a nonmagnetic spacer layer above themagnetic seed sublayer; providing an antiferromagnetic (AFM) layer abovethe spacer layer; and providing a plurality of layers including a pinnedlayer, a reference layer, a barrier layer and a free layer of a readsensor above the AFM layer.
 2. The method of claim 1 wherein the firstpower is from about 30 Watts to about 100 Watts.
 3. The method of claim1 wherein the second power is from about 30 Watts to about 50 Watts. 4.The method of claim 1 wherein the second plasma treatment reduces thethickness of the amorphous FM layer to a thickness of at least 5Angstroms and not more than 20 Angstroms.
 5. The method of claim 1wherein the nonmagnetic spacer layer is deposited to a final thicknessof at least 2.0 Angstroms and not more than 4.0 Angstroms prior todepositing the AFM layer.
 6. The method of claim 1 wherein the secondplasma treatment reduces the thickness of the amorphous FM layer to athickness of at least 5 Angstroms and not more than 20 Angstroms, andthe nonmagnetic spacer is deposited to a final thickness of at least 2.0Angstroms and not more than 4.0 Angstroms.
 7. The method of claim 6wherein the nonmagnetic spacer is deposited to a final thickness of atleast 3.4 Angstroms and not more than 4.0 Angstroms.
 8. The method ofclaim 1 wherein the amorphous FM layer comprises at least one of CoFeB,NiCoFeB, and NiFeB, wherein B comprises from about 18 atomic percent(at. %) to about 22 at. %.
 9. The method of claim 1 wherein the magneticseed sublayer is a bilayer including a first sub layer, the first sublayer on and in contact with the amorphous FM layer, and a second sublayer that is on and in contact with the first sub layer, wherein: thefirst sub layer comprises Ni_(1-x)Fe_(x), where x is at least 0.45 andnot more than 0.55 and the second sub layer comprises Ni_(1-y)Fe_(y)where y is at least 0.05 and not more than 0.15.
 10. The method of claim1 wherein the nonmagnetic spacer layer comprises at least one of Ru, Ti,and Ta.